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These base oils have a high flash point, with closed- cup values > 200°C (ASTM D93) and open-cup values >240° (ASTM D92). Furthermore, the base oils display good cold temperature performance as well, with pour points ranging from -18 °C to -42 °C (ASTM D97). They also provide increased wear protection by decreasing friction and improving overall equipment life as shown in 4-ball wear studies (Figure 2).
Estolides provide excellent oxidative stability by ASTM D2272 RPVOT testing. As illustrated in Figure 3, high viscosity estolides achieved better oxidative stability results than similar viscosity products when tested by RPVOT. With a standard antioxidant ad-pack of 0.5% phenolic and 0.5% aminic antioxidants, estolides outperform most comparable oils of similar viscosity grades, with exceptional performance for the higher viscosity products. This is indicative of a longer lasting fluid life and additionally, less ad-pack may be used to achieve comparable oxidative stability.
the seal. This is useful when dealing with formulations that are causing seal shrinkage or hardness. Base oils offered by Biosynthetic Technologies can be added to the formulation to help balance seal shrinkage and seal swell to develop a complete formulation that meets a target specification.
Figure 4: Hydrolytic stability of Estolides and traditional esters
Proof can be found in the extensive use of estolides in demanding applications. Estolides are currently being used in a variety of industrial and automotive lubricant applications and have garnered recent attention for their use in high-performance motor oil formulations. Biosynthetic Motor Oil was the first certified estolide motor oil formulations (5W-20 and 5W-30) by the American Petroleum Institute (API) which meet industry’s current motor oil standard, API SN-RC (ILSAC GF-5, and now GF-6) while being biodegradable.
Figure 3: Oxidative Stability of Estolides compared to PAOs, PAG, Group III and esters
Estolides also have superior hydrolytic stability. Even at 3 times the recommended test duration, estolide base oils show excellent hydrolytic stability (Figure 4).
Estolide base oils provide superior shear stability compared to other high viscosity base stocks, helping your finished lubricants retain their viscosity, even in severe conditions. They are polar and can slightly swell
Figure 5: Cylinder heads from two Chevy Impala 3.5-liter V6 engines used in an 18-month 150,000-mile field trial in Las Vegas, NV. The conventional motor oil formulation (top, reference engine) had a typical level 19 of varnish at the end of the test, while the estolide formulation (bottom, test engine) and minimal varnish.
In a formulation containing Group II base oil, replacing just 10% of the base stock with an estolide base oil showed significant improvements on the engine
Continued on page 37 LUBE MAGAZINE NO.173 FEBRUARY 2023 35
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